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Relevant Topics on the Strength of Existing Reinforced Concrete Buildings: - In-plane deformability of orthotropic floors - Shear strength of interior beam-column joints under cyclic loads - Seismic retrofitting of a building with strongly different stiffness in the main directions - Destructive and non-destructive tests on concrete - Assessment of the residual strength after fire
No full textThe present research work deals with five important topics relevant to the structural strength of existing Reinforced Concrete (RC) buildings.
The first topic concerns the use of equivalent 2D elements with assigned thickness to reproduce the in-plane deformability of orthotropic floors in the Finite Element (FE) model of the building, for analyses under seismic actions. An advanced FE-based procedure aimed at determining the elastic properties of the homogeneous material constituting the equivalent 2D elements is proposed for the first time. A discussion on the applicability of the simplified procedure commonly adopted by engineers, based on the equivalence between the transverse areas of the RC elements of the real floor and those of the 2D elements, is also provided. A case study in which the simplified procedure is used to effectively reproduce in-plane deformability of floors is presented.
The second topic addressed in this thesis concerns beam-column joint shear behavior under cyclic loads. On the basis of a mechanical analysis and the use of 69 test results available in the literature, a direct formula for the shear strength prediction of interior beam-column joints with deformed bars is proposed. The formula accounts for the resisting contributions of three inclined concrete struts and of joint reinforcements. The influence of the upper column axial load on the inclination of the concrete struts is taken into account. Also a design formula is proposed. On the basis of the model proposed for joints with deformed bars, a shear strength formula and a design formula for beam-column joints with plain bars are also derived.
Another relevant topic addressed herein is the design of the retrofit intervention of an existing RC building whose displacement capacity does not satisfy the seismic Italian Code requirements. The modal analysis highlights that the structure has strongly different translational stiffness along its main directions and low torsional stiffness. To improve the seismic behavior of the building, it is proposed to install an external steel frame with stiff braces along the side of the structure which is the most affected by torsional effect. Conversely, in the orthogonal direction, where the ductility demand is much higher, external steel frames with dissipative braces are used.
Then, the topic concerning the assessment of in-place concrete strength of existing buildings is addressed. The results of an experimental campaign performed on column and cube specimens made with the same concrete mix are presented, to assess the capacity of coring destructive test and non-destructive tests to predict the in-place concrete strength. The non-destructive predictive methods are performed also during the curing of the concrete at different ages. A discussion on drilled cores’ strength, determined using provisions of different building codes, relevant to cube specimens’ strength is provided. The effects of the core diameter and the position of test execution along the columns’ height, on in-place concrete strength, are investigated. The minimum number of cores to adequately predict the in-place concrete strength by means of non-destructive test methods is also determined.
The last topic addressed in this thesis concerns experimental tests to perform for assessing residual strength of RC structures subjected to fire. The test program, with laboratory and in situ tests, used to determine the residual strength of steel reinforcements and concrete of a case study is described. The program includes test methods that are able to catch the variability of concrete degradation with distance from the heated surface. Test results are presented and their acceptability in relation to Italian Code is discussed. A discussion on the advantages and limitations of the adopted test methods, useful for the designers, is performed. To restore the load-bearing capacity of the structure, repair interventions are also proposed.The present research work deals with five important topics relevant to the structural strength of existing Reinforced Concrete (RC) buildings.
The first topic concerns the use of equivalent 2D elements with assigned thickness to reproduce the in-plane deformability of orthotropic floors in the Finite Element (FE) model of the building, for analyses under seismic actions. An advanced FE-based procedure aimed at determining the elastic properties of the homogeneous material constituting the equivalent 2D elements is proposed for the first time. A discussion on the applicability of the simplified procedure commonly adopted by engineers, based on the equivalence between the transverse areas of the RC elements of the real floor and those of the 2D elements, is also provided. A case study in which the simplified procedure is used to effectively reproduce in-plane deformability of floors is presented.
The second topic addressed in this thesis concerns beam-column joint shear behavior under cyclic loads. On the basis of a mechanical analysis and the use of 69 test results available in the literature, a direct formula for the shear strength prediction of interior beam-column joints with deformed bars is proposed. The formula accounts for the resisting contributions of three inclined concrete struts and of joint reinforcements. The influence of the upper column axial load on the inclination of the concrete struts is taken into account. Also a design formula is proposed. On the basis of the model proposed for joints with deformed bars, a shear strength formula and a design formula for beam-column joints with plain bars are also derived.
Another relevant topic addressed herein is the design of the retrofit intervention of an existing RC building whose displacement capacity does not satisfy the seismic Italian Code requirements. The modal analysis highlights that the structure has strongly different translational stiffness along its main directions and low torsional stiffness. To improve the seismic behavior of the building, it is proposed to install an external steel frame with stiff braces along the side of the structure which is the most affected by torsional effect. Conversely, in the orthogonal direction, where the ductility demand is much higher, external steel frames with dissipative braces are used.
Then, the topic concerning the assessment of in-place concrete strength of existing buildings is addressed. The results of an experimental campaign performed on column and cube specimens made with the same concrete mix are presented, to assess the capacity of coring destructive test and non-destructive tests to predict the in-place concrete strength. The non-destructive predictive methods are performed also during the curing of the concrete at different ages. A discussion on drilled cores’ strength, determined using provisions of different building codes, relevant to cube specimens’ strength is provided. The effects of the core diameter and the position of test execution along the columns’ height, on in-place concrete strength, are investigated. The minimum number of cores to adequately predict the in-place concrete strength by means of non-destructive test methods is also determined.
The last topic addressed in this thesis concerns experimental tests to perform for assessing residual strength of RC structures subjected to fire. The test program, with laboratory and in situ tests, used to determine the residual strength of steel reinforcements and concrete of a case study is described. The program includes test methods that are able to catch the variability of concrete degradation with distance from the heated surface. Test results are presented and their acceptability in relation to Italian Code is discussed. A discussion on the advantages and limitations of the adopted test methods, useful for the designers, is performed. To restore the load-bearing capacity of the structure, repair interventions are also proposed
Seismic retrofitting of a reinforced concrete building with strongly different stiffness in the main directions
No full textThe displacement capacity of the existing reinforced concrete building under study does not satisfy the seismic Italian Code require-ments. The modal analysis highlights that the structure has strongly different stiffnesses along its main directions and, in the stiffer one, translation is coupled with torsion. To improve the seismic behavior of the building, it is proposed to install an external steel frame with stiff braces along the side of the structure which is the most deformable due to torsional effect. Conversely, in the orthogonal direction, where the ductility demand is much higher, external steel frames with dissipative braces are used. The effectiveness of the proposed solution is checked by push-over analysis
Experimental and analytical procedure for the stability assessment of brick masonry veneer walls
No full textIn the past, brick masonry veneer walls have been extensively used to construct the external envelope of a wide variety of buildings in different countries around the world. Recently, they have also found application in contemporary building construction. Therefore, these walls are very common in existing buildings. However, brick veneer walls frequently exhibit deficiencies due to poor construction practices or inadequate design. This work presents the most significant investigation methods for identifying such deficiencies. Additionally, it proposes an analytical procedure for assessing the out-of-plane stability of these walls in compliance with the Italian Building Code and the recommendations of UNI EN 1996–1–1:2022. The procedure allows for the easy analysis of masonry walls with openings. Additionally, practical tips for quickly calculating seismic forces on non-structural elements are provided. Then, the proposed procedure and tips are used to assess the masonry veneer walls stability of a recent building with visible damage in the masonry cladding system. The results of the investigation campaign carried out on the veneer walls are provided. The effects of thermal variations on the stability of the masonry veneer walls are also considered. Based on the results of the investigations and analyses, the causes of the damages are identified. To ensure that the brick masonry veneer walls meet the safety requirements prescribed by the standards, interventions are also proposed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Experimental tests for the assessment of residual strength of r.c. structures after fire – Case study
Get PDFA fire in a ham factory in San Daniele del Friuli caused serious damage to the prefabricated reinforced concrete
(r.c.) roof panels and smaller damages to beams, columns and walls. In this paper the data captured during
preliminary inspection of the building structure are described. To determine the residual strength of steel reinforcements
and concrete of r.c. structural elements, a test program with laboratory and in situ tests is presented.
The program includes test methods that are able to catch the variability of concrete degradation with
distance from the heated surface. Test results are presented and their acceptability in relation to Italian Code is
discussed. It is found that the amount of transversal and longitudinal reinforcements strongly influences the
deterioration of the concrete due to fire and, consequently, the strength of structural elements. On the basis of
tests results, a discussion on the advantages and limitations of the adopted test methods useful for the designers is
performed. To restore the load-bearing capacity of the structure, repairs of columns and beams in the first three
bays of the central frame are proposed together with the substitution of the roof over the receiving area
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